The filoviruses, the Ebola and Marburg viruses (EBOVs and MARVs), are NIAID category A priority pathogens which cause highly lethal hemorrhagic fever in humans with fatality rates approaching 90 percent. Identification of therapeutic targets and advancing medical countermeasures for these threats is of high priority. Despite this need, no approved therapeutics are available for filoviral infections. To address this unmet need we propose to develop small molecule therapeutics that specifically target viral innate immune evasion functions and viral transcription. The combination of approaches is expected to yield individual panfilovirus inhibitors with different mechanisms of action, which when combined are expected to act synergistically. Combining inhibitors of viral innate immune evasion with viral transcription inhibitors is particularly appealing, from the point of view of synergy. This is because specific suppression of viral transcription will reduce levels of the IFN-antagonists, while also allowing viral replication to proceed, which is a process that can trigger IFN responses. To achieve these goals, the Center, which consists of a diverse team with extensive experience in filovirus biology, antiviral development and medicinal chemistry, will (1) Develop assays and perform HTS screens to identify and optimize small molecule inhibitors of the EBOV and MARV VP35 IFN-antagonists which function to suppress interferon (IFN)-alpha/beta production in filovirus-infected cells. (2) Develop assays and perform HTS screens to identify and optimize small molecule inhibitors of the filovirus antagonists of IFN-induced Jak-STAT signaling, the EBOV VP24 and MARV VP40 proteins. (3) Develop small molecule inhibitors of EBOV and MARV VP30 dephosphorylation that block viral transcription. (4) Evaluate leads and optimized leads for antiviral activity in cell culture and in animal models, prioritizing those with pan-filoviral potential. The expected outcome of this work is the development of inhibitors of filovirus replication that target viral IFN-antagonists and VP30 dephosphorylation and independently display pan-filovirus efficacy in mouse and guinea pig model. We further expect that these therapeutics will exhibit synergistic activities in vivo.